1. Field of the Invention
The present invention relates to a drive mechanism for driving a movable element linearly along at least one guide shaft.
2. Description of the Related Art
A typical drive mechanism serving as a lens drive mechanism for linearly driving a movable lens includes a lens support frame which holds a lens element and has a pair of bearing arms separate from each other in a direction parallel to the optical axis of the lens; a rack-incorporated member including an engaging portion that is engaged between the pair of bearing arms to be movable relative to the pair of bearing arms in a direction parallel to the optical axis of the lens; a guide shaft which passes through two guide holes formed on the pair of bearing arms, respectively, and further passes through a guide hole formed on the engaging portion of the rack-incorporated member, wherein the two guide holes of the pair of bearing arms and the guide hole of the engaging portion are aligned in a direction parallel to the optical axis of the lens element so that the lens support frame and the rack-incorporated member are linearly guided in the direction of the optical axis of the lens element while being prevented from rotating about the optical axis of the lens element; and a lead screw which extends parallel to the guide shaft, and meshes with teeth formed on the rack-incorporated member, wherein a rotation of the lead screw on its axis causes the rack-incorporated member and the lens support frame to move together in the direction of the optical axis of the lens.
This type of drive mechanism is disclosed in Japanese unexamined patent publication No. 2003-195144.
However, in this lens drive mechanism that is disclosed in Japanese unexamined patent publication No. 2003-195144, backlash occurs between the lens support frame and the rack-incorporated member, which causes a difference in attitude between the lens support frame and the rack-incorporated member relative to the optical axis of the lens element. This difference in attitude becomes a cause of decentering and tilting of the optical axis of the lens element, thus resulting in a deterioration of the optical performance and making it difficult for a position detector to detect the origin point of the lens support frame (the lens element held in the lens support frame).